Hydraulic well control system

ABSTRACT

A system for transmitting hydraulic control signals and hydraulic power to downhole well tools while reducing the number of hydraulic lines installed in the wellbore. Hydraulic control signals can be furnished at relatively lower pressures, and the hydraulic pressure within the line can be selectively increased over a threshold level to provide hydraulic actuation power. The system can provide multiple control paths through a few number of hydraulic lines to provide flexibility and verification of well tool operation. Closed loop hydraulic operation monitors well tool operation, and a combination of pressurized hydraulic lines can provide an operating code for selective downhole well tool control. Four hydraulic lines can provide independent control and actuation of seven well tools, and additional combinations can be constructed.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a system for controlling theproduction of hydrocarbons and other fluids from downhole wells. Moreparticularly, the invention relates to a system for providing hydrauliccontrol signals and power through the same hydraulic line, and forproviding integrated control of multiple well tools with a minimalnumber of hydraulic lines.

[0002] Various tools and tool systems have been developed to control,select or regulate the production of hydrocarbon fluids and other fluidsproduced downhole from subterranean wells. Downhole well tools such assliding sleeves, sliding side doors, interval control lines, safetyvalves, lubricator valves, and gas lift valves are representativeexamples of control tools positioned downhole in wells.

[0003] Sliding sleeves and similar devices can be placed in isolatedsections of the wellbore to control fluid flow from such wellboresection. Multiple sliding sleeves and interval control valves (ICVs) canbe placed in different isolated sections within production tubing tojointly control fluid flow within the particular production tubingsection, and to commingle the various fluids within the commonproduction tubing interior. This production method is known as“comingling” or ““coproduction”. Reverse circulation of fluids throughthe production of tubing, known as “injection splitting”, is performedby pumping a production chemical or other fluid downwardly into theproduction tubing and through different production tubing sections.

[0004] Wellbore tool actuators generally comprise short term or longterm devices. Short term devices include one shot tools and tool havinglimited operating cycles. Long term devices can use hydraulicallyoperated mechanical mechanisms performing over multiple cycles.Actuation signals are provided through mechanical, direct pressure,pressure pulsing, electrical, electromagnetic, acoustic, and othermechanisms. The control mechanism may involve simple mechanics, fluidlogic controls, timers, or electronics. Motive power to actuated thetools can be provided through springs, differential pressure,hydrostatic pressure, or locally generated power.

[0005] Long term devices provide virtually unlimited operating cyclesand are designed for operation through the well producing life. One longterm safety valve device provides fail safe operating capabilities whichcloses the tubing interior with spring powered force when the hydraulicline pressure is lost. Combination electrical and hydraulic poweredsystems have been developed for downhole use, and other systems includesensors which verify proper operation of tool components.

[0006] Interval control valve (ICV) activation is typically accomplishedwith mechanical techniques such as a shifting tool deployed from thewell surface on a workstring or coiled tubing. This technique isexpensive and inefficient because the surface controlled rigs may beunavailable, advance logistical planning is required, and hydrocarbonproduction is lost during operation of the shifting tool. Alternatively,electrical and hydraulic umbilical lines have been used to remotelycontrol one or more ICVs without reentry to the wellbore.

[0007] Control for one downhole tool can be hydraulically accomplishedby connecting a single hydraulic line to a tool such as an ICV or alubricator valve, and by discharging hydraulic fluid from the line endinto the wellbore. This technique has several limitations as thehydraulic fluid exits the wellbore because of differential pressuresbetween the hydraulic line and the wellbore. Additionally, the settingdepths are limited by the maximum pressure that a pressure relief valvecan hold between the differential pressure between the control linepressure and the production tubing when the system is at rest. Theselimitations restrict single line hydraulics to low differential pressureapplications such a lubricator valves and ESP sliding sleeves. Further,discharge of hydraulic fluid into the wellbore comprises anenvironmental discharge and risks backflow and particulate contaminationinto the hydraulic system. To avoid such contamination and corrosionproblems, closed loop hydraulic systems are preferred over hydraulicfluid discharge valves downstream of the well tool actuator.

[0008] Certain techniques have proposed multiple tool operation througha single hydraulic line. U.S. Pat. No. 4,660,647 to Richart (1987)disclosed a system for changing downhole flow paths by providingdifferent plug assemblies suitable for insertion within a side pocketmandrel downhole in the wellbore. In U.S. Pat. No. 4,796,699 to Upchurch(1989), an electronic downhole controller received pulsed signals forfurther operation of multiple well tools. In U.S. Pat. No. 4,942,926 toLessi (1990), hydraulic fluid pressure from a single line was directedby solenoid valves to control different operations. A return means inthe form of a spring facilitated return of the components to theoriginal position. A second hydraulic line was added to provide for dualoperation of the same tool function by controlling hydraulic fluid flowin different directions. Similarly, U.S. Pat. No. 4,945,995 to Thulanceet al. (1990) disclosed an electrically operated solenoid valve forselectively controlling operation of a hydraulic line for openingdownhole wellbore valves.

[0009] Other downhole well tools use two hydraulic lines to control asingle tool. In U.S. Pat. No. 3,906,726 to Jameson (1975), a manualcontrol disable valve and a manual choke control valve controlled theflow of hydraulic fluid on either side of a piston head. In U.S. Pat.Nos. 4,197,879 to Young (1980), and in 4,368,871 to Young (1983), twohydraulic hoses controlled from a vessel were selectively pressurized toopen and close a lubricator valve during well test operations. Aseparate control fluid was directed by each hydraulic hose so that onefluid pressure opened the valve and a different fluid pressure closedthe valve. In U.S. Pat. No. 4,476,933 to Brooks (1984), a pistonshoulder functioned as a double acting piston in a lubricator valve, andtwo separate control lines were connected to conduits and toconventional fittings to provide high or low pressures in chambers onopposite sides of the piston shoulder. In U.S. Pat. No. 4,522,370 toNoack et al. (1985), a combined lubricator and retainer valve wasoperable with first and second pressure fluids and pressure responsivemembers, and two control lines provided two hydraulic fluid pressures tothe control valve. This technique is inefficient because two hydrauliclines are required for each downhole tool, which magnifies the problemsassociated with hydraulic lines run through packers and wellheads.Instead of multiple hydraulic lines, other techniques have attempted toestablish an operating sequence. In U.S. Pat. No. 5,065,825 to Bardin etal. (1991), a solenoid valve was operated in response to a predeterminedsequence to move fluid from one position to another. A check valvepermitted discharge of oil into a reservoir to replenish the reservoiroil pressure. Other systems use electronic controllers downhole in thewellbore to distribute, however the electronics are susceptible totemperature induced deterioration and other reliability problems.

[0010] Multiple hydraulic lines downhole in a wellbore can extend forthousands of feet into the wellbore. In large wellbores having differentproduction zones and multiple tool requirements, large numbers ofhydraulic lines are required. Each line significantly increasesinstallation cost and the number of components potentially subject tofailure. Accordingly, a need exists for an improved well control systemcapable of avoiding the limitations of prior art devices. The systemshould be reliable, should be adaptable to different tool configurationsand combinations, and should be inexpensive to deploy.

SUMMARY OF THE INVENTION

[0011] The present invention provides an apparatus and system fortransmitting pressurized fluid between a wellbore surface and a welltool located downhole in the wellbore. The apparatus comprises at leasttwo hydraulic lines engaged with the well tool for conveying said fluidto the well tool, and means for pressurizing the fluid within thehydraulic lines. The hydraulic lines are capable of providingcommunication control signals to the well tool are further capable ofproviding fluid pressure to actuate the well tool. In differentembodiments of the invention, at least three hydraulic lines are eachengaged with each well tool for selectively conveying the fluid to eachwell tool, and hydraulic control means engaged between said hydrauliclines and each well tool for selectively controlling actuation of eachwell tool in response to pressure changes within selected hydrauliclines.

[0012] The invention also provides a system for controlling at leastthree well tools located downhole in a wellbore. The system compriseshydraulic pressure means for selectively pressurizing a fluid, at leasttwo hydraulic lines engaged with the hydraulic pressure means and witheach well tool for selectively conveying fluid pressure to each welltool, and hydraulic control means engaged between each hydraulic lineand each well tool. Each hydraulic control means is operable in responseto selective pressurization of one or more hydraulic lines by saidhydraulic pressure means, and operation of a well tool through thepressurization of one hydraulic line displaces fluid which is conveyedthrough another hydraulic line.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1 illustrates a two hydraulic line system for providinghydraulic pressure control and power to well tools.

[0014]FIG. 2 illustrates a graph showing a hydraulic line pressure codefor providing hydraulic control and power capabilities through the samehydraulic line.

[0015]FIG. 3 illustrates a three well tool and three hydraulic lineapparatus.

[0016]FIG. 4 shows a representative control code for the apparatus shownin FIG. 3.

[0017]FIG. 5 illustrates a seven well tool and four hydraulic linesystem for providing selective well control and power.

[0018]FIG. 6 illustrates a representative control code for the systemshown in FIG. 5.

[0019]FIG. 7 illustrates another seven well tool and four hydraulic linesystem.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] The invention provides hydraulic fluid control for downhole welltools by uniquely utilizing hydraulics with logic circuitry. Such logiccircuitry is analogous to electrical and electronics systems, anddepends on Boolean Logic using “AND” and “OR” gates in the form ofhydraulic switches. Using this unique concept, digital controlcapability, or “digital-hydraulics” can be adapted to the control ofdownhole well tools such as ICVs.

[0021]FIG. 1 illustrates two hydraulic lines 10 and 12 engaged with pump14 for providing hydraulic pressure to fluid (not shown) in lines 10 and12. Lines 10 and 12 are further engaged with downhole well tools 16 and18 for providing hydraulic fluid pressure to tools 16 and 18. Pump 14can comprise a controller for selectively controlling the fluid pressurewithin lines 10 and 12, and can cooperate with a hydraulic control meanssuch as valve 20 located downhole in the wellbore in engagement withlines 10 and 12, and with tools 16 and 18. Selectively control over thedistribution of hydraulic fluid pressure can be furnished and controlledwith pump 14 at the wellbore surface, or with valve 20 downhole in thewellbore. Control signals to tools 16 and 18 and valve 20 can beprovided within a different pressure range as that required foractuation of tools 16 and 18, and the ranges can be higher, lower, oroverlapping.

[0022]FIG. 2 illustrates one combination of comnmunication and powerfunctions through the same hydraulic tubing, conduit, passage or linesuch as line 10 wherein the control signals are provided at lowerpressures than the power actuation pressures. Pressure is plottedagainst time, and the hydraulic pressure is initially raised above thecommunication threshold but below the power threshold. Within thispressure range, communication signals and controls can be performedthrough the hydraulic line. The line pressure is raised to a selectedlevel so that subsequent powering up of the hydraulic line pressureraises the line pressure to a certain level. Subsequent actuation of thewell control devices, normally delayed as the pressure builds up withinthe long hydraulic tubing, occurs at a faster rate because the line isalready pressurized to a certain level.

[0023] The invention further permits the use of additional hydrauliclines and combinations of hydraulic lines and controllers to provide ahydraulically actuated well control and power system. One embodiment ofthe invention is based on the concept that a selected number ofhydraulic control lines could be engaged with a tool and that controlline combinations can be used for different purposes. For example, athree control line system could use a first line for hydraulic powersuch as moving a hydraulic cylinder, a second line to provide a returnpath for returning fluid to the initial location, and all three linesfor providing digital-hydraulic code capabilities. Such code can berepresented by the following Table: Hydraulic Lines #1  #2  #3  DigitalEquation Numeric Value Lines 0 0 0 0 × 2² + 0 × 2¹ + 0 × 2⁰ = 0 0 0 1 0× 2² + 0 × 2¹ + 1 × 2⁰ = 1 0 1 0 0 × 2² + 1 × 2¹ + 0 × 2⁰ = 2 0 1 1 0 ×2² + 1 × 2¹ + 1 × 2⁰ = 3 1 0 0 1 × 2² + 0 × 2¹ + 0 × 2⁰ = 4 1 0 1 1 ×2² + 0 × 2¹ + 1 × 2⁰ = 5 1 1 0 1 × 2² + 1 × 2¹ + 0 × 2⁰ = 6 1 1 1 1 ×2² + 1 × 2¹ + 1 × 2⁰ = 7

[0024] If “1” represents a pressurized line and if “0” represents anunpressurized line, then the combination of hydraulic lines provides thedescribed code format for a binary communication code. Because thehydraulic line operation can use both a pressurized and an unpressurizedline in a preferred embodiment of the invention, codes 000 and 111 wouldnot be used in this embodiment. However, if one or more lines dischargedfluid to the outside of the line to the tubing exterior, another tool,or other location, codes 000 and 111 would be useful for transmittingpower or signals. If codes 000 and 111 are excluded from use in theinventive embodiment described, the following six codes are availablefor tool control: #1 #2 #3 0 0 1 - 1 0 1 0 - 2 0 1 1 - 3 1 0 0 - 4 1 01 - 5 1 1 0 - 6

[0025] These codes are unique and can be grouped to provide sixindependent degrees of freedom to a hydraulic network. Differentcombinations are possible, and one combination permits the operation ofthree well tools such as ICVs 22, 24, and 26 having double actuatedfloating pistons as illustrated in FIG. 3. Lines 28, 30 and 32 areengaged between pump 14 and ICVs 22, 24, and 26. Lines 28, 30, and 32could provide an opening code 001 for ICV 22. After a sufficient timelapse for all well tools such as the ICVs has occured to detect andregister the 001 code, the line pressure can be raised above the powerthreshold until a selected pressure level is achieved. The pressure canbe held constant at such level, or varied to accomplish other functions.The selected well tool such as ICV 22 is actuated, and return fluid isdirected back through one or more of the lines designated as a “0”,unpressurized line. Next, control line 32 is bled to zero and the entiresystem is at rest, leaving ICV 22 fully open until further operation. Toopen ICV 24, control linesw 28, 30, and 32 can be coded and operated asillustrated. After sufficient time has passed, the system pressure canbe increased to operate ICV 24. The degrees of control freedom andoperating controls can be represented by the following instructions:Hydraulic Line Number 28 30 32 0 0 1 Open ICV 22 0 1 0 Close ICV 22 0 11 Open ICV 24 1 0 0 Close ICV 24 1 0 1 Open ICV 26 1 1 0 Close ICV 26${X = \frac{2^{N} - 2}{2}},\quad {and}$

$X = {\frac{2^{3} - 2}{2} = {3\quad {control}\quad {lines}}}$

[0026] where

[0027] X equals the number of independently controlled ICVs, and

[0028] N equals the number of control lines.

[0029] Another combination is expressed below wherein additional ICVs 34and 36 are added to build a five well tool system. Hydraulic Line Number28 30 32 0 0 1 All ICVs Open 0 1 0 Close ICV 22 0 1 1 Close ICV 24 1 0 0Close ICV 26 1 0 1 Close ICV 34 1 1 0 Close ICV 36

[0030] Z=2^(N)−3, and Z=2³−3=5 control lines

[0031] where

[0032] Z equals the number of dependently controlled ICVs, and

[0033] N equals the number of control lines.

[0034] The number of independently and dependently controlled ICVsprovides system flexibility in the design of an operating system. Forexample, # of Independent ICVs # of Control Lines X = 2^(N) − 2 # ofDependent ICVs N    2 Z = 2″ − 3 1 0  0 2 1  1 3 3  5 4 7 13 5 15  27 631  61 7 63  125  8 127  253 

[0035] From this chart, the feasibility of the concept for one or twohydraulic lines does not offer significant control flexibility oversingle, dedicated hydraulic lines. At three control lines and greater,the benefits of the digital-hydraulic system become apparent assignificant combinations of well control functions are available. Forthe majority of conventional downhole well uses, four control lines areadequate. However, the concepts taught by the invention provideadditionally design flexibility to accommodate additional requirementsas indicated.

[0036] A four ICV digital-hydraulic control system having sevenindependent devices and thirteen dependant devices can operate asfollows: Hydraulic Line Number #1 #2 #3 #4 Independent Dependent 0 0 0 1Open ICV#1 All ICVs open 0 0 1 0 Close ICV#1 Close ICV#1 0 0 1 1 OpenICV#2 Close ICV#2 0 1 0 0 Close ICV#2 Close ICV#3 0 1 0 1 Open ICV#3Close ICV#4 0 1 1 0 Close ICV#3 Close ICV#5 0 1 1 1 Open ICV#4 CloseICV#6 1 0 0 0 Close ICV#4 Close ICV#7 1 0 0 1 Open ICV#5 Close ICV#8 1 01 0 Close ICV#5 Close ICV#9 1 0 1 1 Open ICV#6 Close ICV#10 1 1 0 0Close ICV#6 Close ICV#11 1 1 0 1 Open ICV#7 Close ICV#12 1 1 1 0 CloseICV#7 Close ICV#13

[0037] A representative embodiment of a four hydraulic line system isillustrated in FIG. 5 wherein hydraulic lines 40, 42, 44 and 46 areengaged with controller 48, and are further engaged with hydrauliccontrol means such as module 50 connected to tool 52, module 54connected to tool 56, module 58 connected to tool 60, module 62connected to tool 64, module 66 connected to tool 68, module 70connected to tool 72, and module 74 connected to tool 76. Selectivepressurization of lines 40, 42, 44 and 46 selectively operates one ormore of such seven well tools according to a programmed code asrepresented in FIG. 6. For example, a code of “0010”, wherein all linesare unpressurized except for the pressurization of line 44, operates toclose tool 52 as illustrated.

[0038] Each hydraulic control means or control mechanism can be designedwith a combination of valves and other components to perform a desiredfunction. Referring to FIG. 3, control mechanism 78 includes two controlmodules 80 and 82 each located on opposite sides of the floating pistonwithin ICV 22. Control module 80 includes check valve engaged with line32, and further includes check valve 84 engaged with pilot operatedvalves 86 and 88. Pilot operated valve 86 is engaged with line 30, andpilot operated valve 88 is engaged with line 28. Check valves 90 and 92and pilot operated valves 94 and 96 are positioned as shown in FIG. 3for control module 82. Similar combinations of modules and internalcomponents are illustrated in FIG. 5 and in FIG. 7 for differentoperating characteristics.

[0039] The unique combination of valves and other components within eachcontrol module provides for unique, selected operating functions andcharacteristics. Depending on the proper sequence and configuration,pressurization of a hydraulic line can actuate one of the tools withoutactuating other tools in the system. Alternatively, various combinationsof well tools could be actuated with the same hydraulic line if desired.

[0040] By providing communication and power capabilities through thesame hydraulic lines, the invention significantly eliminates problemsassociated with pressure transients. In deep wellbores, the hydrauliclines are very long and slender, which greatly affects the hydraulicline ability to quickly transmit pressure pulses or changes from thewellbore surface to a downhole tool location. In deep wellbores, five totell minutes could be required before the hydraulic lines wereaccurately coded for the communication of sequenced controls. If some ofthe ICVs were located relatively shallow in the wellbore, such ICVswould receive the code long before other ICVs located deep in thewellbore. This configuration could cause confusion on thedigital-hydraulics control circuit.

[0041] This problem can be resolved by dedicating certain lines forcommunication signals and other lines for power. Alternatively, apreferred embodiment of the invention utilizes such time delaycharacteristics by applying the communication coding early at relativelylow pressures where the ICVs receive the codes but are not activated,and then the pressure is increased above a selected activation thresholdto move the ICVs. This permits communication and power to be transmittedthrough the same hydraulic lines, and further uses the communicationpressures to initially raise the line pressures to a selected level andto shorten the power up time required.

[0042] For another instruction, pistons within all ICV can be moved in adirection from the initial position toward a second position, and can bemaintained above second position pressure. The device response initiallydirects the control line pressure to the second side of the pistonactuator. As the piston responds to the force created by thedifferential pressure, fluid on the low pressure side is displaced intothe tubing. The device eventually strokes fully and attains the secondposition, and the fluid will slowly bleed away.

[0043] Another embodiment of the invention is illustrated below wherecertain lines are dedicated as power lines and other lines are dedicatedas communication control lines. A representative sequence code for afive line tool system can be expressed as follows: Power LinesCommunication Lines #1 #2 A B C Independent Dependent 0 1 0 0 0 OpenICV#1 All ICVs closed 1 0 0 0 0 Close ICV#1 Open ICV#1 0 1 0 0 1 OpenICV#2 Open ICV#2 1 0 0 0 1 Close ICV#2 Open ICV#3 0 1 0 1 0 Open ICV#3Open ICV#4 1 0 0 1 0 Close ICV#3 Open ICV#5 0 i 0 1 1 Open ICV#4 OpenICV#6 1 0 0 1 1 Close ICV#4 Open ICV#7 0 1 1 0 0 Open ICV#5 Open ICV#8 10 1 0 0 Close ICV#5 Open ICV#9 0 1 1 0 1 Open ICV#6 Open ICV#10 1 0 1 01 Close ICV#6 Open ICV#11 0 1 1 1 0 Open ICV#7 Open ICV#12 1 0 1 1 0Close ICV#7 Open ICV#13 0 1 1 1 1 Open ICV#8 Open 1CV#14 1 0 1 1 1 CloseICV#8 Open ICV#15 5 Lines, 8 ICVs 5 Lines, 15 ICVs

[0044] Although more lines are required to control a certain number ofwell tools, this embodiment of the invention provides certain designbenefits. Response time within the lines can be faster, a singlepressure level can be utilized, and any possibility of confusion betweena communication pressure code and a power pressure code is eliminated.

[0045] The invention is applicable to many different tools includingdownhole devices having more than one operating mode or position from asingle dedicated hydraulic line. Such tools include tubing mounted ballvalves, sliding sleeves, lubricator valves, and other devices. Theinvention is particularly suitable for devices having a two-way piston,open/close actuator for providing force in either direction in responseto differential pressure across the piston.

[0046] The operating codes described above can be designed to provide astatic operating code where the fluid pressures stabilize within eachhydraulic line. By providing for static pressures at different levels,communication control signals can be provided by the presence or absenceof fluid pressure, or by the fluid pressure level observed. For example,different pressure levels through one or more lines can generatedifferent system combinations far in excess of the “0” and “1”combinations stated above, and can provide for multiple combinations atleast three or four time greater. In effect, a higher order ofcombinations is possible by using different line pressures incombination with different hydraulic lines. Alternatively, the operationof a single line can be pulsed in cooperation with a well tool or ahydraulic control means operation, or can be pulsed in combination withtwo or more hydraulic lines to achieve additional control sequences.Such pulsing techniques further increase the number of systemcombinations available through a relatively few number of hydrauliclines, thereby providing maximum system capabilities with a minimumnumber of hydraulic lines.

[0047] Although the preferred embodiment of the invention permitshydraulic switching of the lines for operation of downhole well toolssuch as ICVs, switching functions could be performed with various switchtechniques including electrical, electromechanical acoustic, mechanical,and other forms of switches. The digital hydraulic logic described bythe invention is applicable to different combinations of conventionaland unconventional switches and tools, and provides the benefit ofsignificantly increasing system reliability and of permitting areduction in the number of hydraulic lines run downhole in the wellbore.

[0048] The invention permits operating forces in the range above 10,000lb. and is capable of driving devices in different directions. Such highdriving forces provide for reliable operation where environmentalconditions causing scale and corrosion increase frictional forces overtime. Such high driving forces also provide for lower pressurecommunication ranges suitable for providing various control operationsand sequences.

[0049] The invention controls a large number of downhole well toolswhile minimizing the number of control lines extending between the toolsand the wellbore surface. A subsurface safety barrier is provided toreduce the number of undesirable returns through the hydraulic lines,and high activation forces are provided in dual directions. The systemis expandable to support additional high resolution devices, can supportfail safe equipment, and can provide single command control or multiplecontrol commands. The invention is operable with pressure or no pressureconditions, can operate as a closed loop or open loop system, and isadaptable to conventional control panel operations. As an open loopsystem, hydraulic fluid can be exhausted from one or more lines or welltools if return of the hydraulic fluid is not necessary to the wellboreapplication. The invention can further be run in parallel with otherdownhole wellbore power and control systems. Accordingly, the inventionis particularly useful in wellbores having multiple zones or connectedbranch wellbores such as in multilateral wellbores.

[0050] Although the invention has been described in terms of certainpreferred embodiments, it will become apparent to those of ordinaryskill in the art that modifications and improvements can be made to theinventive concepts herein without departing from the scope of theinvention. The embodiments shown herein are merely illustrative of theinventive concepts and should not be interpreted as limiting the scopeof the invention.

what is claimed is:
 1. An apparatus for transmitting pressurized fluidbetween a wellbore surface and a well tool located downhole in thewellbore, comprising: at least two hydraulic lines engaged with the welltool for conveying said fluid to the well tool, wherein said hydrauliclines are capable of providing communication control signals to the welltool, and wherein said hydraulic lines are further capable of providingfluid pressure to actuate the well tool; and means for pressurizing thefluid within said hydraulic lines to provide said communication signalsand said fluid actuation pressure.
 2. An apparatus as recited in claim1, further comprising a controller at the wellbore surface forselectively pressurizing said hydraulic lines.
 3. An apparatus asrecited in either claim 1 or claim 2, wherein said communication controlsignals comprise a lower pressure than said fluid pressure for actuatingthe well tool.
 4. An apparatus as recited in any preceding claim,wherein said communication control signals are provided in a pulsedsequence.
 5. An apparatus as recited in any preceding claim, whereinsaid communication control signals are provided in a static codeidentified by the presence of a selected fluid pressure.
 6. An apparatusas recited in any preceding claim, wherein at least three well tools areeach engaged with two or more hydraulic lines, further comprising aswitch engaged with said hydraulic lines and said well tools foractuating one of the well tools by the selective pressurization of onehydraulic line.
 7. An apparatus as recited in any preceding claim,wherein at least three well tools are each engaged with two or morehydraulic lines, further comprising a switch engaged with said hydrauliclines and said well tools for actuating one of the well tools by theselective pressurization of two hydraulic lines.
 8. An apparatus asrecited in any preceding claim, wherein said hydraulic lines are capableof providing well tool actuation pressure, after communication controlsignals are transmitted to the well tool, by increasing the fluidpressure in at least one hydraulic line.
 9. An apparatus as recited inany preceding claim, wherein said hydraulic lines form a closed loop forreturning fluid to the wellbore surface, further comprising means fordetecting the return of fluid through one hydraulic line when anotherhydraulic line is pressurized.
 10. An apparatus as recited in anypreceding claim, wherein one of said lines is dedicated to providecommunication control signals.
 11. An apparatus as recited in anypreceding claim, wherein one of said lines is dedicated to provide fluidpressure to actuate the well tool.
 12. An apparatus for transmittingpressurized fluid between a wellbore surface and three well toolslocated downhole in the wellbore, comprising: at least three hydrauliclines each engaged with each well tool for selectively conveying thefluid to each well tool; and control means engaged between saidhydraulic lines and each well tool for selectively controlling actuationof each well tool in response to pressure changes within selectedhydraulic lines.
 13. An apparatus as recited in claim 12, wherein saidcontrol means comprises a hydraulic control means.
 14. An apparatus asrecited in either claim 12 or claim 13, wherein the well tools areactuable in two directions from opposing positions of the well tool, andwherein said control means comprises two control modules separatelyengaged with said opposing well tool positions so that each controlmodule is capable of providing selective fluid flow in two directionsrelative to the well tool.
 15. An apparatus as recited in claim 14,wherein each control module comprises a hydraulic circuit having a checkvalve for resisting fluid flow from the tool direction and incommunication with one of said hydraulic lines, and further comprises apilot operated valve engaged with said hydraulic line and with the toolwhich is closed in an initial condition and is actuatable by a fluidpressure increase in one of said other hydraulic lines.
 16. An apparatusas recited in claim 15, further comprising another pilot operated valveengaged with said hydraulic line and with the tool which is closed in aninitial condition and is actuatable by a fluid pressure increase in thethird of said hydraulic lines.
 17. An apparatus as recited in claim 16,further comprising a check valve engaged in series with said pilotoperated valve between a hydraulic line and the tool.
 18. An apparatusas recited in any of claims 12 to 17, wherein said hydraulic lines arefurther capable of providing fluid pressure to actuate the well tool.19. A system for controlling at least three well tools located downholein a wellbore, comprising: hydraulic pressure means for selectivelypressurizing a fluid; at least two hydraulic lines engaged with saidhydraulic pressure means and with each well tool for selectivelyconveying fluid pressure to each well tool; and hydraulic control meansengaged between each hydraulic line and each well tool, wherein eachhydraulic control means is operable in response to selectivepressurization of one or more hydraulic lines by said hydraulic pressuremeans, and wherein operation of a well tool through the pressurizationof one hydraulic line displaces fluid which is conveyed through anotherhydraulic line.
 20. A system as recited in claim 19, further comprisinga controller for detecting said displaced fluid conveyed through ahydraulic line during operation of a well tool.
 21. A system as recitedin claim 20, wherein said controller is capable of measuring thedisplaced fluid conveyed through said hydraulic line.
 22. A system asrecited in any of claims 19 to 21, wherein the number of hydraulic linesengaged with said hydraulic pressure means and with each well tool isequal to the number of well tools located downhole in the wellbore. 23.A system as recited in any of claims 19 to 22, wherein each well tool isuniquely operable by the pressurization of a unique combination of saidhydraulic lines.
 24. A system as recited in claim 23, wherein saidhydraulic control means prevent operation of other well tools notresponsive to the pressurization of said unique combination of hydrauliclines.
 25. A system as recited in either claim 23 or claim 24, whereinsaid unique combination of pressurized hydraulic lines represents asignature code formed by pressurized and unpressurized hydraulic lines.26. A system as recited in claim 25, wherein said pressurized hydrauliclines contain fluid pressure above a selected pressure, and wherein saidunpressurized hydraulic lines contain fluid pressure below a selectedpressure.
 27. A system as recited in either of claim 25 or claim 26,wherein the selected pressure is the same for at least two hydrauliclines.
 28. A system as recited in any of claims 19 to 27, wherein saidhydraulic pressure means is capable of providing hydraulic fluid powerto a well tool through one of said hydraulic lines.
 29. A system asrecited in claim 28, wherein the well tool comprises a sliding sleeve.30. A system as recited in any of claims 19 to 29, wherein saidhydraulic pressure means is capable of reducing hydraulic pressure for apressurized fluid below a selected pressure, and wherein said hydrauliccontrol means is capable of preventing further movement of thecorresponding tool following such pressure reduction.